The present invention is directed generally to an ink absorber for use primarily in an ink jet printer. More particularly, the present invention is directed to a composite non-woven material for use as an ink-absorber in an ink jet printer. More specifically, the present invention is directed to a composite non-woven needlefelt for use as an ink absorber in an ink jet printer. The composite non-woven ink absorber has a low density/coarse denier top layer and a high density/fine denier bottom layer wherein denier is understood to be the weight-per-unit-length measure of the fiber. The composite non-woven ink absorber of the present invention provides for uniform and efficient absorption and transportation of ink from the top surface of the top layer to the body of the bottom layer of the composite non-woven material.
In ink jet printing devices, the print head typically includes one or more ink filled channels, each with a relatively small ink supply chamber at one end and having an opening, referred to as a nozzle, at the opposite end. Ink droplets are formed and are discharged onto a substrate to be printed. To prevent the nozzles from becoming clogged with dried residual ink droplets, the nozzles are thoroughly flushed with additional ink jet droplets after use. Alternatively, a vacuum may be created within the nozzles, which removes all residual ink prior to any further printing operations. The waste ink generated by either the flushing or vacuuming procedure is discharged to a waste ink absorber where it is subsequently stored for the duration of the service life of the ink jet printer.
Another consideration is the use of xe2x80x9cfull bleedxe2x80x9d ink jet photographic quality printing. An overshoot of ink droplets from a print head can intentionally be made to fill the print sheet from edge-to-edge. The print sheet would not be adhered to a base sheet but would be independently fed through the ink jet printer. The overshoot of ink droplets in the xe2x80x9cfull bleedxe2x80x9d process would be dispersed to a waste ink absorber where it is subsequently stored or transferred to a final waste ink reservoir for the duration of the service life of the ink jet printer.
In both cases, the collection of ink is not always uniform. Ink accumulates on the surface of the waste ink absorber device. It dries into a gel state that consequently clogs the waste ink absorber. The clogged waste ink absorber does not allow for efficient and uniform dispersal of waste ink into the body of the waste ink absorber. This results in an insufficient capacity for waste ink storage with respect to the life of the ink jet printer.
Nozzles can become contaminated or even clogged by contact with the waste ink. The print sheet can have unwanted ink spots on its non-printed backside. In either case, the quality of print is greatly reduced because of the accumulation of the ink in the waste ink absorber.
There is a need for a waste ink absorber that will eliminate waste ink clogging in the waste ink absorber and which will also allow for a sufficient amount of waste ink storage corresponding to the service life of an ink jet printer. The composite non-woven ink absorber, in accordance with the present invention, overcomes the limitations of the prior art. It is a substantial advance in the art.
It is an object of the present invention to provide an ink jet absorber for use primarily in an ink jet printer.
Another object of the present invention is to provide a non-woven ink jet absorber.
A further object of the present invention is to provide a composite non-woven needlefelt for use as an ink jet absorber.
Yet a further object of the present invention is to provide an ink jet absorber that accomplishes the uniform and efficient absorption and transport of ink from a top surface of the composite non-woven material to the body of the composite non-woven material.
The ink jet absorber in accordance with the present invention utilizes a composite non-woven material, such as a composite non-woven needlefelt, having a low density/coarse denier top layer and at least one higher density/finer denier lower or bottom layer. The denier is understood to be the weight-per-unit-length of the fiber used to form the non-woven needlefelt. The ink jet absorber is intended primarily for use with ink jet printers, and will be discussed hereinafter in that context. It is to be understood that the ink jet absorber of the present invention is susceptible of other uses.
The ink jet absorber quickly absorbs waste ink discharged from ink jet nozzles and, through the inherent capillary gradient between layers in the composite non-woven material, disperses or transports the waste ink evenly from the surface of the top layer through to the bottom layer of the ink jet absorber. Typically, waste ink from ink jet nozzles is dropped onto the ink jet absorber at a specific point on the surface of the top layer. The ink jet absorber of the present invention will quickly disperse waste ink vertically through its top layer and will then subsequently disperse the waste ink evenly horizontally through the bottom layer of the ink jet absorber.
One important characteristic of the present invention is the provision of a capillary gradient between the top and bottom layers of the composite non-woven material. The capillary gradient is accomplished by constructing a composite non-woven material, such as a composite non-woven needlefelt, in the subject ink jet absorber, with a minimum of two layers having differing capillary forces between these layers. The capillary force of each layer is selected in accordance with the requirements of the specific application. The ink jet absorber of the present invention has a top layer consisting of a low density/coarse denier composition and at least a high density/fine denier composition bottom layer.
Capillary force in a non-woven material is a function of the surface tension of ink with respect to fiber type, contact angle of ink on the fiber and the fiber surface area per unit volume of the non-woven material, such as needlefelt. Capillary force in a non-woven material can be considered as being analogous to capillary head in a vertical capillary tube. The space between the fibers in the non-woven material can be approximated as a vertical capillary tube. The equation for force in a vertical capillary tube is given as follows:
F=2xcfx80r"sgr"LV cos xcex8LS where,
F=Capillary Force
r=Tube Radius
"sgr"LV=Surface Tension
xcex8LS=Contact Angle
The fiber surface area per unit volume of the non-woven material is a function of the non-woven material""s density and fiber size. The equation for fiber surface area per unit volume of the non-woven material is given as follows:   SA  =            (              4                  d          f                    )        ⁢          (              ρ                  ρ          f                    )      
where,
SA=fiber surface area per unit volume
df=diameter of fiber
xcfx81=density of non-woven needlefelt
xcfx81f=density of fiber
A higher SA or surface area will create many individual capillary tubes within the non-woven material, such as a needlefelt, thus creating a high capillary force, F, in the non-woven needlefelt. A low density/coarse denier layer will have a low fiber SA or surface area per unit volume of felt compared to a high density/fine denier layer. The ink jet absorber of the present invention has a top layer consisting of a low density/coarse denier composition and at least a bottom layer consisting of a high density/fine denier composition. The top layer can be considered as having a high permeability, or xe2x80x9copenxe2x80x9d structure, while the bottom layer can be considered as a having a low permeability with a high capillary force particularly in the horizontal direction. High permeability is understood to mean a low fiber surface area to unit volume structure and low permeability is understood to mean a high fiber surface area to unit volume structure.
The xe2x80x9copenxe2x80x9d structure of the top layer of the composite non-woven needlefelt or similar material ink absorber of the present invention allows the waste ink from ink jet nozzles to quickly move vertically or to be transported from the top surface of the low density/coarse denier composition top layer through to the high density/fine denier composition bottom layer. Since the dwell time of the waste ink is minimized at the top surface of the top layer of the ink absorber, and ink absorption is uniform in the bottom layer, the possibility of ink build-up at the top surface of the top layer is minimized. Ink build-up can cause clogging of the ink jet absorber and unwanted contact between the built-up ink and ink jet printer nozzles.
The construction of the composite non-woven material is such that the fibers of the top layer and bottom layers are physically in contact. In one embodiment they may be interlocked by the action of, for example, a needle loom. Preferably, the fiber interlock will be unidirectional with fibers residing in the top layer being driven into and interlocked with fibers in the bottom layer. The attachment of each layer in this type of construction utilizes well-established interlocking techniques and therefore is economical. This contributes to an overall reduction in manufacturing costs.
While a needlefelt induced fiber interlock is particularly suited for use in forming the composite non-woven ink absorber in accordance with the present invention, other connections between the layers of the non-woven material are also within the scope of the present invention. The non-woven layers could be laminated and secured by a pressure sensitive adhesive strip bond. Alternatively, a dot style pressure sensitive adhesive bond could also be utilized. A thin, highly permeable layer of a low melt polyester non-woven fiber could be used to secure the layers. The layers could also be unsecured but placed in physical contact. Each one of the non-woven fiber layers is also preferably formed as a needlefelt material, as that term is understood in the art. It is to be understood that other materials, typically other non-woven materials which are not needlefelt materials, and also other materials, which may not be non-woven materials are also useable in the present invention. The term needlefelt will be used subsequently but will be understood as encompassing these other arrangements.
The composite non-woven needlefelt for use as a waste ink absorber in accordance with the present invention is to be used in a unidirectional manner in which the waste ink from ink jet nozzles enters the top surface of the top layer. If necessary, the unidirectional configuration of this composite non-woven needlefelt is accomplished by distinctly defining the differentiation of layers via fiber color selections. The distinction between the top and bottom layers via fiber color selection eliminates the need for critical fit and function inspection. This contributes to an overall reduction in manufacturing cost.
The composite non-woven ink absorber in accordance with the present invention provides an effective, efficient device for absorbing and holding waste ink in an ink jet printer. It is a substantial improvement over the prior art devices and is a significant advance in the art.